The present invention relates to semiconductor devices, methods of forming the same, and methods of operating the same. More particularly, the present invention relates to NAND-type nonvolatile memory devices having a stacked structure, methods of forming the same, and methods of operating the same.
A NAND-type nonvolatile memory device connects predetermined numbers of cells to NAND-type logic to increase an integration density of an array. Because a contact number in a cell array. in a NAND-type memory device is considerably less than that of a comparable NOR-type device, a size of a chip may be relatively small. Accordingly, the demand for NAND-type nonvolatile memory devices generally increases in accordance with high-integration and large-capacitance trends of semiconductor memory devices.
A conventional NAND-type nonvolatile memory device includes cell arrays in a first layer on the semiconductor substrate. However, in accordance with high-integration and large-capacitance trends of semiconductor memory devices, a size of cell arrays realized on a flat surface of the first layer is becoming smaller and the number of cell arrays is simultaneously increasing. Accordingly, as high-integration and large-capacitance progress according to the limits of photolithography processing, it may be difficult to realize cell arrays in the first layer of a NAND-type nonvolatile memory device.